implies a Kelt. **ésmesi, a confusion of pres. *smesi and fut. *ésomesi. The W. 2nd pl. ych is, as usual, a new form made to match.
As byẟaf used for the fut., wyf has lost its fut. meaning except in certain idioms, as yr wyfyno yfory ' I shall be there to-morrow '.
§ 180. The Imperfect—i. As above intimated, § 171 ii (2), the W. impf. comes from the Ar. optative. This was formed by means of a suffix *‑ii̯ē‑, *‑i̯ē- with secondary endings.
ii. (1) In athematic verbs the suffix *‑i̯ē- was F-grade and accented in the sg.; the preceding vowel had R- or V-grade; thus 3rd sg. Gk, τιθείη < *dhi-dhe-i̯ēt (ei̯ R1e of ēi̯), Skr. dadhyā́t < *dhe-dh‑i̯ḗt, the Skr. preserving the original accentuation.
(2) In Kelt. the ē became ī, so that the forms would be *‑a-i̯ī́t, *‑e‑i̯ī́t; these were levelled as *‑i‑i̯ī́t in Brit. and this gives ‑ai, § 75 iv, v (2); thus Kelt. *kara-i̯ī́t > W. carai ‘would love’. This form would also result from the 1st and 2nd sg. forms *‑a-i̯ēm, *‑a-i̯ēs; hence the endings for those persons were selected from thematic verbs.
(3) The consonant stem *es‑ ‘be’ gave Ar. *s‑(i)i̯ē‑t, which gives Skr. siyā́t or syā́t, O. Lat. siet; in Kelt. it would be *sii̯ī́t. Coming generally after a preverb, or after its complement, it was unaccented; and *´siiīt gives regularly W. (h)oeẟ ‘would be, was’ § 75 iv (2); the h- is seen in yttoeẟ < *yd-hoeẟ < *íta sii̯īt ‘there would be’ § 219 ii. The whole tense oeẟwn etc. was built from the 3rd sg.
iii. (1) In thematic verbs the suffix ‑i̯ē‑ had its V-grade ‑i̯‑, which formed a diphthong with the thematic vowel, which was always ‑o‑; thus the optative of *bhérō ‘I bear’ was sg. 1. *bhéroi̯‑m̥ > Skr. bháreyam (for *bharayam). In Kelt. it would be *béroi̯‑m̥ > Brit. *béroi-an(n) > W. *cy-merw͡y‑n > cymerwn. The only possible explanation of ‑wn is that it is for *‑w͡yn, see § 78 i (2); on *oi > w͡y § 75 ii (2); on the retention of ‑n § 113 i (1).
(2) The W. 2nd sg. ‑ud comes regularly from the 2nd sg. middle *‑oi-thēs. The ending *‑thēs (: Skr. ‑thāḥ) is represented in the ‑the‑r of Ir. deponents; and ‑ud spread from deponent to all verbs in W. because it was distinctive.
iv. (1) In athematic verbs, in the middle voice where the ending was syllabic, the suff. became R-grade *‑i̯ə‑; this coming before the accent remains as ‑i̯a‑; thus in the deponent verb gwnn ‘I know’ the 3rd sg. impf. is gwyẟi̯ad for *gwẟi̯ad regularly representing the 3rd sg. opt. mid. *u̯id-i̯ə-tó.
(2) In long-vowel stems the reduced stem-ending and suffix would thus be *ə-i̯ə; by § 63 vii (5) this should give *ii̯ə > ‑ī‑, which is the usual form (though other reductions are possible), as in Skr. da-dī-tá < *de-dī-to, √dō‑. Thus the 3rd sg. opt. mid. of Kelt. *karā-mi would be *kar-ī-tó, which gives regularly W. cerid, the impers. of the imperf. ind. This middle was undoubtedly a passive in Kelt., and was assimilated in its use to the impers. pres. in ‑r after the ‑r form for this tense, namely *‑ir, had gone out of use owing to its clashing with the pres.